Feeding the globe's growing population will be challenging in coming decades as climate change is expected to impact agricultural production and crop yields, scientists say.

The problem is especially worrisome as food production will need to double by 2050 to feed an expected population of nine billion, which is two billion more than the planet's current population, says Jerry Hatfield, who directs the National Laboratory for Agriculture and the Environment.

Feeding those billions "is going to take some changes in terms of minimizing climate disruption," he said at the American Association for the Advancement of Science's annual meeting.

Those disruptions are expected to include volatility of rainfall, more drought and rising temperatures with global warming, all of which will have an impact on crop yields, he said.

"If you look at production from 2000 to 2050, we basically have to produce the same amount of food as we produced in the last 500 years," he said.

However, he warned, increasing both land use levels and crop yields will have a deteriorating effect on soils.

Other scientists at the meeting presented further warnings on the need to deal with climate change, and especially with rising temperatures in America's Midwest, the country's vital grain-producing region, where the biggest risk to food security is drought.

"If you look at the future projection for the Midwest, we have high confidence that temperatures will increase by quite a bit," said Kenneth Kunkel, a U.S. National Oceanic and Atmospheric Administration climatologist.

The 21st century could see drought conditions worse than anything seen for centuries, the scientists warned.

With the majority of the world's grain production centered in regions vulnerable to global warming, there is worry over "trends that are a little bit concerning" including a reduction in the global grain reserves needed to provide society with an important food safety net, said James Gerber, an agricultural scientist at the University of Michigan.

An increased use of GMO crops could ease the situation, he suggested.

Summing up, Paul Ehrlich, head of Stanford University's Center for Conservation Biology, said solving the crisis would require a "real social and cultural change over the entire planet."

"If we had a thousand years to solve it, I would be very relaxed, but we may have 10 or 20 years," he said.